The invention relates to a servomotor actuated by a pressure medium, comprising a piston reciprocatable in a cylinder and a piston rod brought out at one side, the piston being movable relatively to the piston rod and its central portion being for this purpose arranged between annular faces on the piston rod.
A known servomotor of this kind (U.S. Pat. No. 31 58 072) has a long stroke. The piston has a small diameter and a long axial length. By reason of these dimensions, it is well guided in the cylinder. Since the piston is secured to the piston rod with the interpositioning of elastic rings, it can move at will relative to the piston rod. There is therefore no danger of the piston jamming if the free end of the piston rod that carries the piston moves out of centre because the piston rod is guided in only one end wall of the cylinder.
Under otherwise identical conditions, however, the small piston diameter requires a comparatively high actuating pressure and the length of the piston contributes considerably to the cylinder length, which is particularly significant in the case of servomotors with a short stroke.
The invention is based on the problem of providing a servomotor of the aforementioned kind which, under otherwise identical prerequisites, can be driven at a lower pressure and made of a shorter length.